This invention relates to a long-lived electrophotographic photoreceptor and an electrophotographic process therefor.
Previously, selenium has been used extensively in electrophotographic photoreceptors. In recent years, the use of organic photoreceptors and amorphous silicon photoreceptors has been grown increasingly. When electrophotographic photoreceptors are processed by the Carlson method, each of steps as charging, exposure, development, transfer, erasure and cleaning is a factor to cause deteriorations of the photoreceptors. Especially, various flaw and wear generated in copying progress are the most significant factor that determines the life of electrophotographic photoreceptors. Therefore, it has been proposed that a protective layer is disposed on the surface of an electrophotographic photoreceptor or that the photoconductive layer is made from amorphous silicon having high hardness [cf., for example, Japanese Patent Unexamined Application No. Sho. 54-86341].
However, if the previous proposed electrophotographic photoreceptors are installed in copiers or printers, flaws occurs unavoidably during the copying progress on account of sliding contact with the particles of toner, carrier or any foreign matter that develop as a result of paper jams. Especially, an electrophotographic photoreceptor having an object to be a longer life have to endure accidents as mentioned above encountered during the copying progress in order to improve reliability thereof. Examples of flaws occurred by the accident include cracks developed only in the photoconductive layer, damage penetrated into a support, and dents occurred in the photoconductive layer. Since these flaws occur by accident, their development mechanism is not completely clear. However, in many cases, it is postulated that the cause is insufficient strength of either the photoconductive layer or the support, for example, the heretofore used aluminum substrate [cf. Japanese Patent Unexamined Application Nos. Sho. 61-159544, Sho. 61-9547 and Sho. 62-142740].
Another factor considered to determine the life of amorphous silicon base photoreceptors is the development of image defects such as black or white spots occurring on account of film imperfections. It is known that film imperfections develops as convex image defects with sized of 30 .mu.m and more.
Film imperfections are caused by reasons including the deposition of dirt particles before film formation and the sticking of dust particles during film formation and other causes that are equally important are in many causes related to the constituent material of substrates and the method of their treatment, as exemplified by materials defects in the substrate and the projections that left unremoved as a result of finish-working [T. Fukuda, S. Shirai, K. Saitoh and H. Ogawa, Optoelectronics, Vol. 4, p. 273 (1989)].